In a laser light source provided with a laser resonator configured so that a reflection mirror and an output mirror are disposed so as to be opposed to each other with a laser medium placed therebetween, stimulated emission light emitted from an excited laser medium is reflected by the reflection mirror, while a part of the stimulated emission light passes through the output mirror and the remaining part thereof is reflected therefrom. Laser oscillation is produced by reciprocation of the stimulated emission light between the reflection mirror and the output mirror. Laser oscillation light which passes through the output mirror and is output to the outside generally becomes such that some transverse modes are overlapped thereon.
However, in accordance with usage, there are cases where it is required that the laser oscillation light output from the laser light source is subjected to only the fundamental mode as the transverse mode, or, there are cases where it is required that the laser oscillation light is subjected to only another specific transverse mode.
The invention disclosed in Patent Document 1 intends that the laser oscillation light of a specific transverse mode is selectively output from a laser resonator. The laser light source disclosed in this document is provided with a discontinuous phase element on the resonance light path in the laser resonator. The discontinuous phase element gives phase variations to respective positions in the section of a light beam for the stimulated emission light reciprocating in the laser resonator. The discontinuous phase element has a thickness distribution and gives a phase variation distribution corresponding to the thickness distribution to the stimulated emission light, wherein the transverse mode of the laser oscillation light is determined.